Endless reinforcement and method for producing same

ABSTRACT

An endless reinforcement which comprises a plurality of unitary strips including a multiplicity of continuous cords with the strips being positioned across the width of the reinforcement from one side to the other at opposing angles to the edges of the reinforcement with successive lengths of the strips being folded with respect to each other at the edges to form a generally zigzag pattern. Also, a method for producing such a reinforcement and a tire therewith as well as the resulting tire.

. United States Patent 1191 Greene et al. 1 Nov. 6, 1973 [541 ENDLESSREINFORCEMENT AND METHOD 2,982,327 5/1961 Vanso et al 152/361 FORPRODUCING SAME 3,550,667 12/1970 Bartley 152/361 3,563,296 3/1971 Wells152/361 [751 In nt rs: Charles Greene; George C- 3,024,828 3/1962 Smithet al... 152/301 Varner, both of Spartanburg, S.C. 3,598,166 10/1971Wells 152/361 3,422,874 l/l969 Weitzel.... 152/361 [731 Asslgnee: MResearch 3,024,829 3/1962 Cooper .1 152/361 Corporation, Spartanburg,S.C. 22 Filed; Oct 13 1972 Primary ExaminerDrayton E. Hoffman AssistantExaminer-Robert Saifer [21] Appl. No.: 297,508

Related U.S. Application Data Division of Ser. No. 90,560, Oct. 18,1970, Pat. No.

u.s. c1. .-1s2/3611 R, 152/354 Int. Cl. 1360c 9/20 Field 0fSearch....161/58, 99, 104,-

l6l/71, 86, 92, 93, 98, 144,165; 156/175, 181,v 177, 326; 152/354, 355,356, 361

References Cited UNITED STATES PATENTS 6/1971 Varner 152/361Att0rney-Norman C. Armitage et al.

[57] ABSTRACT An endless reinforcement which comprises a plurality ofunitary strips including a multiplicity of continuous cords with thestrips being positioned across the width of the reinforcement from oneside to the other at opposing angles to the edges of the reinforcementwith successive lengths of the strips being folded with respect to eachother at the edges to form a generally zigzag pattern. Also, a methodfor producing such a reinforcement and a tire therewith as well as theresulting tire.

1 Claim, 8 Drawing Figures PATENIEUnuv 61975 3370.042

SHEEIUUF 7 l ENDLESS REINFORCEMENT AND METHOD FOR i PRODUCING SAME Thisis a division of application Ser. No. 90,560, filed Nov. 18, 1970, nowU.S. Pat. No. 3,720,570.

The tire industryrecently has developed considerable interest in tireconstructions which include an annular reinforcement belt or breakerabout the periphery of the tire between the tread and the carcass. Suchbelted tires have the advantage of better road stability and longertread life both in radial and bias ply constructions.

The reinforcements generally are formed of inextensible thread or cordcoated with or embedded in a suitable insulating material such asrubber, plastic or some other resinous material. The cords usually aredisposed in a pattern in which portions thereof extend in differentdirections to each other and in direction biased with respect to thelongitudinal axis of the reinforcement. This may be accomplished by biascutting woven fabric which has been calendered with a layer ofunvulcanized rubber. Since such reinforcements of necessity are splicedand have a large number of cut ends at each edge, it has been proposedto form reinforcements by winding one or more continuous lengths of cordonto a rotating drum while employing a reciprocating guide to traversethe drum surface and to lay the cord in a generally zigzag patternthereon. Examples of such reinforcements are disclosed in U. S, Pats.Nos. 2,982,327 and 3,422,874. I

One of the considerations in the design of the reinforcment is theeffect of the outermost layer on the creation of lateral forces in tiresmade with such reinforcements. This effect is evidentwhen tires aremounted on a vehicle or on a test wheel under load. With tires includingbias cut woven fabric reinforcements the lateral-forces are all in onedirection while with certain wound continuous cord reinforcements, thelateral invention provides a novel method for producing suchreinforcements and tires therewith.

The endless reinforcement of the presentinvention comprises a pluralityof unitary strips including a multiplicity of continuous cords with thestrips being positioned across the width of the reinforcement from-oneside to the other at opposing angles to the edges of the reinforcementwith successive lengths of the strips being folded with respect to eachother at the edges to form a generally zigzag pattern. The summation ofthe areas in which cords are disposed at one angle is sub stantiallyequal to the summation of the areas in which cords are disposed at anopposing angle for a full width portion of the outer surface of thereinforcement constituting between about and percent of the total outersurface area.

The reinforcement of the invention minimizes the lateral forces of thetire in which it is incorporated by sub stantially equalizing the areasof different cord direction over the foot print of the tire. The footprint" is the area of the tire in contact with the road when the tire ismounted on a vehicle. Generally, the foot print" comprises between about5 perc and 15 percent of the total surface area of the tire periphery.

The endless reinforcement of the invention preferably is formed bypositioning two unitary strips in substantial mirror image dispositionwith respect to a plane circumferentially bisecting the reinforcement.Thus, transversely disposed points on corresponding strip lengths arelocated substantially equidistant from the edges of the reinforcementand from the bisecting plane. With certain strip patterns, hereinafterillustrated, the strips may be disposed in a more forward or rearwardposition circumferentially to provide for equal spacing of the strips inthe finished reinforcement.

The endless reinforcement usually is of a generally cylindrical form orconfiguration and is made from conventional tire cord materials such asfiber glass, rayon, polyester, nylon, cotton, metal wire and similartype cords, although the benefitsand advantages of the invention areparticularly apparent with materials such as fiber glass, metal wire,etc., which are easily abraded or degraded by cord to cord contact. Thedimensions of the reinforcement may be varied over a considerable rangedepending upon the ultimate use thereof. For example, withreinforcements which are to be applied to tire carcasses in flat bandform, the circumference will be considerably smaller than the finalcircumference in the finished tire. Likewise, the original width will besubstantially larger than the final width. This is due to the fact thatduring the expansion step in the forming of the tire, the circumferenceof the reinforcement generally will be substantially increased and thewidth will be significantly reduced. During this expansion, the angle ofthe cord across the width of the reinforcement from one side to theother as measured from the edge will be reduced substantially. Withreinforcements which are applied to a carcass that has already beenformed into the shape of a torus, i.e., a doughnut shape similar to thatof the final tire, the dimensions will be more nearly the same in theoriginal form as applied to the carcass and in the final size in thefinished tire.

As pointed out above, the endless reinforcement of the invention isformed from a plurality of unitary strips including a' multiplicity ofcontinuous cords associated with rubber, plastic or a similar material.Although the configuration of the individual strip generally isrectangular with the cords in a single plane and equally spaced fromeach other, the cords may be unequally spaced and/or disposed in morethan one plane. Also, the cords may be of different sizes or differentmaterials, e.g.', the end cords may be rayon with the intermediate cordsbeing metal wires or other combinations of different cords. Likewise,heavier rubber coatings may be used at certainportions across the widthof the strip or along the length. thereof as desired. While the stripgenerally will have a smooth outer rubber surface, indentations oropenings through the strip may be utilized.

The strip employed in the reinforcement of the invention advantageouslyis formed by passing a plurality of cords in the desired spacedrelationship through an extruder, although other methods maybe employed.For example, a number of parallel cords or a cord fabric may becalendered with rubber and then slit into strips of the desired width.In addition, the strip may be formed by coating a plurality of cordswith a rubber latex in a multiple dip operation to form a unitary strip.

Prior to the formation of the reinforcement, the rubber of the strip maybe partially or totally vulcanized.

The width of the strip may vary over a considerable range and generallyis between about A and 2 2Q inches and preferably between about and l V;inches to facilitate convenient handling and reinforcement construction.The particular width selected will depend upon belt size and thereinforcement pattern desired. For example, with some applications suchas large offthe-road machinery, the strip width may be up to six inchesor more.

The employment of the strip in the production of the reinforcement ofthe invention permits closer cord spacing than is ordinarily attainablewhen reinforcements are made from single cords. Thus, cord spacing ofabout 18 to 30 or 40 cords per inch of strip width may be employed,depending upon cord size, without cord to cord contact occurring in thereinforcement. However, wider cord spacing of IO cords per inch or lessmay be advantageous under some conditions.

The reinforcement preferably is formed from a minimum number of stripsso that the number of cut ends in the reinforcement is minimized. If thecomplete reinforcement is formed from two continuous strips, the ends ofthe strips are the only cut ends in the reinforcement. With certainreinforcement designs, it may be desirable to form the reinforcementfrom more than two strips with each strip being of the same or differentwidth and length. This facilitates the production of a reinforcement ina shorter period of time and/or produces a reinforcement with adifferent pattern. Such patterns may be desired to produce belts havingparticular characteristics such as a higher degree of symmetry and thelike. In either construction, the reinforcement of the invention isendless, thus eliminating overlapping or splices which can lead toimbalance and possible premature failure of a tire.

As pointed out above, the strips are positioned across the width of thereinforcement from one side to the other at opposing angles to the edgesin the generally zigzag pattern. With'reinforcements intended to beexpanded, the initial angle of the strips and the cord therein isgenerally in the range of about 50 to 80 and preferably about 50 to 60as measured from an edge of the reinforcement. During expansion, theangle of the strips and cord usually will be reduced to an angle anglein portions of the strips adjacent to the edges of v the reinforcementmay be greater or less than the angle in the center portion. Such aconstruction may be advantageous where different reinforcement expansioncharacteristics are desired for particular shapes or types of tires.

In the reinforcement of the invention, the strips are folded at theedges of the reinforcement. Upon folding of the strips, the succeedinglengths of the strips are positioned in the zigzag pattern atapproximately the same angles with respect to one edge as the previouslength of each strip prior to the fold is with respect to the oppositeedge. This provides a symmetrical cord position in the finalreinforcement and minimizes the possibility of imbalance in the tire. Ifdesired, the strips can be preconditioned, e.g., prefolded, prior to theformation of the endless reinforcement.

The strips may be associated with a green or unvulcanized rubber layerto form the reinforcement. This may be accomplished by forming thestrips in their generally zigzag pattern over the surface of such arubber layer or band. Also, a rubber layer may be placed over the outersurface instead of or together with a second rubber layer on the insidethereof. It may be desirable in some constructions to provide rubbershoulder portions adjacent the edges of the reinforcement. Such shoulderportions can be used alone or in combination with one or more rubberlayers. The shoulder portions assist in the elimination of entrapped airand in the positioning of the reinforcement with respect to the carcassso that the edges will be properly disposed in the final tire inrelation to the center portion of the reinforcement. Such shoulderportions are particularly useful in the production of tires in which itis desirable that the reinforcement be disposed equidistant from thetread surface at all points across the width thereof.

The reinforcement of the invention made with two or more strips eachcontaining a multiplicity of cords provides a novel structure with areduced number of crossovers, that is, points at which a cord transfersfrom one surface of the reinforcement to another, adjoining a cordtransferred in the opposite direction. This reduction in cross-overs isparticularly important in reinforcements employing cord elements whichmay be damaged by cord to cord contact. A further advantage of thestructure of the invention is that the transfer of the strips from onesurface of the reinforcement to the other does not result in anysignificant thickening of the belt cross section as may occur withsingle cord reinforcements. Also, the use of unitary strips decreasesthe production time for a reinforcement as compared with single cordconstructions. In addition, the cord spacing may be significantlydecreased without increasing production time.

The invention will be further illustrated with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic illustration of one embodiment of an endlessreinforcement of the invention showing a portion of the strip pattern ofthe outer surface and the cord direction within the strips;

FIG. 2 is a schematic illustration of a portion of the pattern of thepartially'formed reinforcement of FIG. 1;

FIG. 3 is a schematic illustration showing the sequence of strippositioning at 'the beginning of the winding cycle of the reinforcementof FIG. 1;

FIG. 4 is a schematic illustration of another embodiment of an endlessreinforcement of the invention showing a portion of the strip pattern ofthe outer surface and the cord direction within the strips;

FIG. 5 is a schematic illustration of a portion of the pattern of thepartially formed reinforcement of FIG.

FIG. 6 is a schematic illustration showing the sequence of strippositioning at the beginning of the winding cycle of the reinforcementof FIG. 4;

FIG. 7 is a fragmentary schematic view of a tire including an endlessreinforcement of the invention; and

FIG. 8 is a schematic illustration of one form of apparatus for formingan endless reinforcement of the invention.

Portions of typical endless reinforcements in accordance with theinvention are shown in FIGS. 1-7 of the drawings. The reinforcement.illustrated in FIGS. ll-3 is similar to the reinforcement shown in FIGS.4-6 except that the strip pattern is different. As shown in FIG. 2,strips 11 and 12 are disposed in a zigzag repeating pattern withsucceeding lengths of the strips being displaced from the precedingones. The reversal points or folds 13 and 14 form the edges of thereinforcement. The starting positions of the strips 11 and 12 arelocated at points along the edges of the reinforcement which aredisposed transversely across the width of the reinforcement. Likewise,succeeding folds of each strip are disposed transversely with respect toeach other. In FIG. 3 a simple guide means 17 has strip guide heads 18and 19 which are movable with respect to the surface on which thereinforcement is wound. Longitudinal movement of the surface while theguide means is moved transversely positions the strips at an angle withrespect to the surface.

To provide a lay down as shown in FIG. 2, initially only strip 11 isdeposited as guide means 17 moves from position A to position B.Thereafter, guide means 17 moves from position B to position C, and thefeeding of strip 12 through guide head 19 is begun while feeding ofstrip 11 is continued. Succeeding lengths of strips 11 and 12 are fedthrough the guide heads 18 and 19 respectively until guide head 18returns to its starting position where the feeding of strip 11 throughguide head 18 is stopped and the feeding of strip 12 through guide head18 is continued for one last traverse across the reinforcement to thestarting point of strip 12. This completes the reinforcement. FIG. 1shows the strip .pattern of the outer surface and the direction of thecords within the strips. The lined strip portions represent cords in onedirection and the blank portions represent cords in the other direction.

The endless reinforcement 20 shown in FIGS. 4, 5 and 6 is formed in thesame manner as that described above. However, the pattern of thereinforcement shown in FIG. 4 is different from that shown in FIG. 1 inthat the reinforcement of FIG. 4 has fewer diamondshaped areas acrossthe width' of the reinforcement, one less than the pattern of FIG. 1.With this construction, the starting positions of the strips aredifferent from those shown in FIG. 2. As shown in FIGS. 5 and 6 of thedrawings, the starting point of strip 22 is displacedcircumferentiallyfrom the starting point of the strip 21, a distance equal to the lengthof the fold. The reinforcement of FIG. 4 is formed in the mannerdescribed above employing a similar guide means 17 having guide heads18' and 19'. The reinforcement is formed using guide means 17 by feedingonly strip 21 through guide head 18' on the first transverse fromposition A to position B and then feeding both strips 21 and 22 throughguide heads 18' and 19 respectively until guide means 18' returns to thestarting position of strip 21 after which the last length of strip 22 ispositioned to complete the reinforcement. Alternatively,v

strips 21 and 22 can be started at the same edge of the reinforcement asshown by the dotted line of strip 22 from position Ato position B ofguide means 17'. The strip pattern of the outer surface of the completereinforcement is shown in FIG. 4.

FIG. 7 shows a section through a tire including a reinforcement of theinvention with a reinforcement 26 movement on rod 34 for laying strips29 and 30 is desired zigzag patterns on drum surface 32. Drum 31 andguide means 33 are driven by a power source shown as motor 35. Motor 35is drivingly connected through a belt and pulley arrangement 36 to arotatable shaft 37. Shaft 37 is connected to a barrel cam 38 and todrive shaft 39 for drum 31 through a suitable gear train 40. A camfollower 42 connected to the strip guide 33 engages a groove 38a in thesurface of cam 38. Groove 38a is of such a configuration that duringrotation of the winding drum 31, guide 33 reciprocates across drumsurface 32 transversely to the direction of rotation so that strips 29and 30 are laid in a zigzag pattern over surface 32, the strips beingfolded back on themselves at the edges of the reinforcement.

Gear train includes a gear mechanism 43 to control the positioning ofthe strips on drum surface 32 during the subsequent rotation of the drum31 so the strips being laid on the surface are in a predeterminedposition with respect to other strip lengths. This control of the striplay down provides for the achievement of the desired pattern in thereinforcement and provides for the formation of a completereinforcement, i.e., a belt in which the strip spacing and configurationis substantially uniform and in accordance with the preselected pattern.

In a preferred procedure for forming a reinforcement of the inventionemploying the apparatus shown in FIG. 6, winding drum 31 is continuouslyrotated to draw unitary strips 29 and 30 including a multiplicity oftire cords (not shown) over guides 44 and 45, through guide 33 and ontodrum surface 32. Simultaneously,

' the guide 33 reciprocates with respect to the surface of the drum 31to lay the strips in a zagzag pattern on the surface thereof. As guide33 approaches an edge of the drum surface, the movement of the guide isreversed by the cam 38 so as to fold the strips back on themselves andprovide a reversal of the strip pattern across the surface 32 in anopposite direction. The relationship of the speed of rotation of thedrum 31 with respect to the movement of guide means 33 determines thestrip pattern of the reinforcement. The winding of the strips on thesurface is continued until the pattern is completed. In this way anendless reinforcement is formed from two continuous strips.

The invention willbe described in greater detail with reference to thefollowing examples which are intended to illustrate the inventionwithout restricting the scope thereof.

EXAMPLE I' eter, seven revolutions of the drum with 4 5/7 cycles of thecord guide per drum revolution, one cycle being a traverse across thedrum and back.

The endless reinforcement is applied to a flat band tire carcass andtread and sidewall-forming rubber stock is placed over the breaker. Theflat band assembly is shaped in the form of a torus under heat andpressure and vulcanized to form a tire. During the shaping process thecircumference of the reinforcement is increased to about 90 inches andthe width thereof reduced to about 4.6 inches. The cord angle is about26 as measured from an edge.

EXAMPLE [I The procedure of this example is the same as that of ExampleI except that the width of the reinforcement is 9.0 inches. A beltsimilar to that shown in FIG. 4 is formed from two rubber covered cordstrips each 0.75 inches wide and 0.06 inches thick containing 14 brassplated steel cords about 0.024 inches in diameter, after 6 drumrevolutions with 4 5/6 cycles of the cord guide per revolution.

EXAMPLE ill The procedure of this example is the same as that of ExampleI except that the reinforcement has a circumference of 120 inches, awidth of 7.2 inches and a strip angle of 24. A reinforcement is formedafter 7 revolutions of the drum with 3 5/7 cycles of the guide per drumrevolution, from strips each 0.94 inches wide and 0.06 inches thickcontaining 18 brass plated steel cords 0.024 inches in diameter. Thisreinforcement is used in a tire retreading operation by applying thereinforcement over a tire from which the tread has been buffed.Thereafter, tread stock is applied over the belt, and the assembly isvulcanized to form a retread truck tire.

The above description, drawings and examples show that the presentinvention provides a novel reinforcement for a pneumatic tire whichovercomes the disadvantages of bias-cut fabric reinforcements and theproblems of endless cord reinforcements heretofore known. Theconstruction of the reinforcement of the invention substantiallyeliminates cord to cord contact during manufacture and use which canresult in premature tire failure. The reinforcement of the inventionprovides a high degree of flexibility in-the configuration anddimensions which can be employed. Furthermore, the reinforcement of theinvention is useful both for new tires and for retread tires. For newtires the reinforcement of the invention not is only useful in radialtype tires where the reinforcement is applied after the carcass isshaped into the form of a torus, but also the belt is particularlysuitable for use in tires made by flat band building methods in whichthe reinforcement is applied to the carcass in flat band form andexpanded during the carcass shaping procedure. A further advantage ofthe reinforcement of the invention is the high degree of balance andabsence of lateral forces which can be achieved in tires incorporatingthe reinforcement. This is due to the disposition of the strips withrespect to one another and the fact that the reinforcement is without asplice. Also the reinforcement does not contain separate plies which cancreate shear planes and transverse forces or side-thrust in a runningtire.

While the above description has been directed primarily to an endlessreinforcement for various types of tires it will be apparent that thepresent invention may be utilized to provide reinforcements for otherendless reinforced products such as drive belts, conveyor belts,snow-mobile belts and similar products. Also, the reinforcement of theinvention is useful for the production of other cord components of atire, for example, for the carcass itself or for a unitizedbreaker/carcass assembly. The reinforcement can be wound over a carcassor applied thereto in fiat band form and expanded, e.g., to produce abelted bias ply tire, or wound over or applied to an expanded carcasssuch as in the production of a radial ply tire. Furthermore, thereinforcement can be used with a tire from which the tread has beenremoved, new tread stock applied and vulcanized to form a retread tire.

It will be apparent to one skilled in the art that various modificationsand variations in the procedures, materials and apparaus can be madewithin the scope of the invention. For example, while a singlereinforcement will generally replace a conventional two-ply breakerbelt, more than one reinforcement or a reinforcement of extra thicknessmay be advantageous in certain applications. Therefore, the foregoingdescription, drawings and examples are intended to illustrate thepreferred embodiments of the invention, and scope of the invention is tobe limited only by the following claims.

That which is claimed is:

l. A tire having a carcass and a tread, said tire including an endlessreinforcement which comprises a plurality of unitary strips includingamultiplicity of continuous cords with the strips being positioned acrossthe width of the reinforcement from one side to the other at opposingangles to the edges of the reinforcement and with successive lengths ofthe strips being folded at the edges to form a reinforcement with agenerally zigzag pattern and a substantially uniform cross-sectionwherein the strips are positioned in substantially mirror imagerelationship to a circumferentially bisecting plane through saidreinforcement in a plurality of wraps with successive wraps being spacedfrom each other and with the cords of said strips being in contiguousrelationship throughout the entire length of said strips, and thesummation of the areas in which cords are disposed atone angle beingsubstantially equal to the summation of the areas in which cords aredisposed at an opposing angle for a full width portion of the outersurface of the reinforcement constituting between about 5 and 15 percentof the total'outer surface area.

1. A tire having a carcass and a tread, said tire including an endless reinforcement which comprises a plurality of unitary strips including a multiplicity of continuous cords with the strips being positioned across the width of the reinforcement from one side to the other at opposing angles to the edges of the reinforcement and with successive lengths of the strips being folded at the edges to form a reinforcement with a generally zigzag pattern and a substantially uniform cross-section wherein the strips are positioned in substantially mirror image relationship to a circumferentially bisecting plane through said reinforcement in a plurality of wraps with successive wraps being spaced from each other and with the cords of said strips being in contiguous relationship throughout the entire length of said strips, and the summation of the areas in which cords are disposed at one angle being substantially equal to the summation of the areas in which cords are disposed at an opposing angle for a full width portion of the outer surface of the reinforcement constituting between about 5 and 15 percent of the total outer surface area. 